Clubhead Vane Pump With Balanced Vanes

ABSTRACT

The subject matter of this specification can be embodied in, among other things, a fluid pump that includes a housing with a cam block. The pump also includes a collection of vanes, each having a shank having a leading edge and a trailing edge, and a head having a curved outer side. The pump also includes a rotor having a collection of slots, each slot having substantially parallel leading and trailing edges spaced to accommodate the shank of one of the vanes, wherein each vane contacts the cam block at a contact point on the head controlled by the rotor slot position and the head outer curved surface, the contact point being located relative to the shank edge when the vane is radially aligned with the major and minor radii, and located rotationally to create a radial force between the head curved surface and the cam block.

TECHNICAL FIELD

This instant specification relates to dual-lobe vane style positive displacement high pressure (HP) pumps.

BACKGROUND

Dual lobe vane style positive displacement high pressure (HP) pumps, such as the example pump 100 shown in FIG. 1, utilize a collection of vanes 102 having a crown radius with a center on the central plane of the vane. Each of a collection of vanes 102 is contained within a corresponding rotor slot 104 centered about a radial line which passes through the center of a rotor 106, e.g., the center of rotation. The rotor 106 and vanes 102 are then contained inside a cam 108 and axially between two port plates (not shown). The rotor 106, vanes 102, cam 108, and port plates are sandwiched between two backing plates (not shown) which contain porting passages to interface with a housing (not shown) allowing the separation of an inlet flow from an outlet flow. The rotor 106 is supported on a shaft 112 which in turn is supported by bearings (not shown) typically mounted in the two backing plates, although other bearing arrangements are possible. The port plates and the cam 108 are axially sandwiched by the backing covers which are axially retained either by fasteners, e.g., bolts, pressure loading, or both. A collection of pumping chambers 114 are formed by two adjacent vanes 102, a cam inside surface 110, the rotor 106 outside radius and the port plate axial surfaces. The pumping action is created by the change in the length of the radius on the inside surface 110 of the cam 108 between a smaller radius 120, e.g., minor radius, and a larger radius 122, e.g., major radius.

The rotor 106 is rotated by the shaft 112 and urges the vanes 102 to rotate relative to the cam 108. The vane 102 is urged into contact with the cam 108 inner surface at the peak of the crown radius to form a sliding seal with the cam inside surface 110 completing the pumping chambers 114. The rotor 106 contains radial slots 104 which allow radial movement of the vanes 102 allowing the vanes 102 to follow the cam 108 inner surface as they are rotated by the rotor 106. The rotor vane slots 104 have terminal cavities 116 at the inboard end to provide clearance for the vanes 102 as they move radially as the vanes follow the cam inside surface 110.

The port plates incorporate flow passages (not shown) to connect the under-vane terminal cavities 116 to the inlet and discharge passages as appropriate. This porting typically assures that the vanes 102 see the same pressure on the tips and the bottoms in the inlet and discharge arcs. In the inlet and discharge arc the leading and trailing vane 102 faces, e.g., relative to the direction of rotation of the rotor 106, will be exposed to the same pressure, e.g., both at discharge pressure or both at inlet pressure. In major dwell arcs the vane 102 faces will see discharge pressure on the leading face and inlet pressure on the trailing face. In minor dwell arcs the vane 102 faces will see inlet pressure on the leading face and discharge pressure on the trailing face. In the major and minor dwell arcs the conventionally balanced vanes control the geometry so that the peak of the crown radius (seal point) occurs at the centerline plane of the vane 102 tip and results in high pressure on approximately 50% of the vane 102 tip. In the major dwell the high pressure is applied from the centerline plane to the leading edge of the vane 102. In the minor dwell the high pressure is applied from the centerline plane to the trailing edge of the vane 102. This results in a radial pressure imbalance of approximately 50% of the vane 102 thickness times the vane 102 width that positively loads the vane 102 into the cam inner surface 110. At the balance point at the center of the vane 102, the pressure differential on either face of the vane 102 reverses between the major and minor dwells, e.g., the discharge pressure is on the leading face in the major dwell and trailing face in the minor dwell. The centripetal force due to the mass of the vane 102 being rotated adds to the radial hydraulic imbalance force, increasing the vane 102 contact force on the cam inner surface 110. In the inlet and discharge arcs, dynamic forces due to acceleration from the radial motion and centripetal forces acting on the mass of the vane 102 and frictional forces can further increase the vane 102 contact force on the cam inner surface 110 since the vanes 102 are hydraulically balanced.

In the conventionally balanced vane 102 the 50% hydraulic imbalance and high centripetal force generally results in relatively high stresses in the major and minor dwell arcs when the inlet pressure contacts over half the vane 102 tip and discharge pressure contacts the bottom of the vane 102. The contact in the inlet and discharge arcs is substantially lower since there is relatively little hydraulic imbalance.

Another design consideration is the location and movements of the contact point on the crown radius relative to the vane 102 centerline plane as the vane 102 is rotated through the inlet, major dwell, discharge arc and the minor dwell. The contact point of the vane 102 crown radius to the cam inner surface 110 is the common tangency point of the two radii of curvature of the surface 110. Conceptually, this point is established by a line that passes through the center point that the cam 108 is generated from and the center point of the vane 102 tip crown radius. The movement of the contact point is driven by combinations of vane geometry, crown radius, rotor slot location, vane tipping in the rotor slot 104, and in the inlet and discharge arcs, the cam 108 tangency radii at the point of contact. The conventionally balanced vane 102 contact point is typically on the rotational centerline plane in the major and minor dwell arcs and at the maximum departure from this plane at the mid points of the inlet and discharge arcs since the cam 108 surface radii is varying between the major and minor radii in these arcs. In addition the pressures acting on the vane 102 faces in a circumferential direction and cam 108 to vane 102 tip frictional forces vary through rotation of the vane 102 in the various arcs and cause the vane 102 to either tip backward, forward or parallel to the rotor slot 104 edges.

A number of prior designs have added a circumferential extension beyond the main radial shank of the vane giving the vane a “club head” or inverted ‘L” cross-sectional, as are described in U.S. Pat. No. 3,711,227, U.S. Pat. No. 3,054,357, and U.S. Pat. No. 7,637,724.

A number of designs have altered the vane tip geometry to cause the seal point to be at or near the leading edge of the vane 102 in the major and minor dwell arcs. Such designs are described by U.S. Pat. No. 3,711,227 and U.S. Pat. No. 7,637,724.

SUMMARY

In general, this document describes dual-lobe vane style positive displacement high pressure (HP) pumps.

In a first aspect, a fluid pump includes a housing having an inlet port and an outlet port, a cam block having an inner surface comprised of two minor radii different from two major radii on the common center axis, and four developed curved surfaces connecting the two minor radii with the two major radii. The fluid pump also includes a collection of vanes, each vane having a vane shank having a leading shank edge and a trailing shank edge, and a vane head having a curved outer side, the curved side in contact with the cam block inner surface to separate a corresponding high fluid pressure region of a collection of high pressure regions from a corresponding low pressure region of a collection of low pressure regions. The fluid pump also includes a rotor having a central axis substantially aligned with the center axis of the cam block inner surface and including a collection of vane slots, each vane slot having a leading slot edge, a trailing slot edge substantially parallel to the leading slot edge, and spaced apart from the leading slot edge to accommodate the vane shank of one of the collection of vanes, a cavity at the radial inboard side of each slot forming a fluid path within the vane slot, and fluid flow passages axially disposed on each side of the cam block with fluid passages communicating with the housing inlet and outlet ports and cavities formed by the cam inner surface, the rotor outside diameter and adjacent vanes and rotor cavities at the inboard side of each vane slot, wherein each vane of the collection of vanes contacts the cam block inner surface at a contact point on the vane head controlled by the rotor vane slot position and the vane head outer curved surface, the contact point being located relative to the vane shank edge when the vane is radially aligned with the major radius and minor radius, and the contact point being located rotationally to create a controlled radial force between the vane head curved surface and the cam block inner surface.

Various embodiments can include some, all, or none of the following features. For each vane of the collection of vanes, the vane shank can have a vane longitudinal axis that is offset from the central axis of the rotor. For each vane of the collection of vanes, the leading shank edge can be substantially parallel to the leading slot edge when the vane is radially aligned with the minor radius, and the leading shank edge is tipped in the vane slot such that it is not parallel to the leading slot edge when the vane is radially aligned with the major radius. An upper end of the vane shank can be in contact with one of the leading slot edge or trailing slot edge, and a lower end of the vane shank can be in contact with the other of the leading slot edge or the trailing slot edge. For each vane of the collection of vanes, the vane head can extend away from the trailing shank edge at an angle substantially perpendicular to the trailing shank edge. The rotor can also include a collection of fluid ports, each of the collection of fluid ports in fluid communication between a cavity of a vane slot and a high pressure fluid region of the collection of high pressure regions, substantially adjacent to the cavity. The curved outer side can be generated from an axis located on the leading edge of the vane shank. The leading slot edge can be substantially in radial alignment with the central axis. The curved outer side can be generated from an axis offset a predetermined distance in a direction of rotation from the leading slot edge.

The systems and techniques described here may provide one or more of the following advantages. First, a system can provide high pumping efficiency. Second, the system can operate with reduced internal stresses and friction. Third, the system can provide increased performance and/or pump lifespan.

The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional diagram of an example prior art vane pump.

FIG. 2 is a cross-sectional diagram of an example balanced clubhead vane pump.

FIGS. 3A and 3B are close-up cross-sectional diagrams of an example balanced clubhead vane pump.

FIG. 4 is a cross-sectional diagram of another example balanced clubhead vane pump.

FIGS. 5A and 5B are close-up cross-sectional diagrams of another example balanced clubhead vane pump.

FIG. 6 is a cross-sectional diagram of another example balanced clubhead vane pump.

FIG. 7 is a cross-sectional diagram of another example balanced clubhead vane pump.

DETAILED DESCRIPTION

This document describes examples of clubhead vane fluid pumps that include substantially balanced vanes. The example pumps use predetermined vane geometries, predetermined rotor slot geometries, and club-shaped vane tip features that, in some embodiments, can reduce internal stresses and wear, and/or improve pump performance.

FIG. 2 is a cross-sectional diagram of an example balanced clubhead vane pump 200. The pump 200 is a dual lobe vane style positive displacement high pressure (HP) pump. The pump 200 includes a collection of clubhead vanes 202, each of the clubhead vanes 202 being located within a corresponding rotor slot 204 formed about the periphery of a rotor 206. The rotor 206 and vanes 202 are contained inside a cam 208.

The rotor 206 and vanes 202 of the example balanced clubhead vane pump 200 are located between two port plates (not shown). The rotor 206, vanes 202, cam 208, and port plates are placed between two backing plates (not shown) which contain porting passages to interface with a housing (not shown), allowing the separation of an inlet flow from an outlet flow. The rotor 206 is supported on a shaft 212 supported by bearings (not shown), mounted in the two backing plates, although in some embodiments other support and/or bearing arrangements are possible. The port plates, the cam 208, and the backing covers are axially retained either by fasteners, e.g., bolts, pressure loading, or both.

A collection of pumping chambers 214 of the example balanced clubhead vane pump 200 are formed by two adjacent vanes 202, the inside surface 210 of the cam 208, the outside surface 230 of the rotor 206 and the port plate axial surfaces. The pumping action is created by the change in length of the radius between the center of the shaft 212 and the inside surface 210 of the cam 208 between a shorter length radius 220, e.g., a minor radius, and a longer length radius 222, e.g., a major radius.

The inside surface 210 of the example balanced clubhead vane pump 200 may be conceptually divided into eight zones. Two inlet arcs 240, positioned approximately 180 degrees opposite each other in which the length of the radius between the center of the shaft 212 and surface 210 increases from the minor radius to the major radius cause an increasing volume in the pumping chambers 214. Two discharge arcs 242 positioned approximately 180 degrees opposite each other in which the length of the radius between the center of the shaft 212 and surface 210 decreases from the major radius to the minor radius cause a decreasing volume in the pumping chambers 214. Two major dwell arcs 244 are positioned approximately 180 degrees opposite each other situated between the inlet arcs 240 and the discharge arcs 242 in which the length of the radius between the center of the shaft 212 and surface 210 remains a constant at the major radius, e.g., little or no volume change in pumping chambers 214. Two minor dwell arcs 246 are positioned approximately 180 degrees opposite each other situated between the discharge arcs 242 and the inlet arcs 240 in which the length of the radius between the center of the shaft 212 and surface 210 remains a constant at the minor radius, e.g., little or no volume change in pumping chambers 214.

The major dwell arcs 244 and the minor dwell arcs 246 of the example balanced clubhead vane pump 200 provide a substantially sealed chamber between inlet and discharge. The port plates include porting surfaces (not shown) on their periphery that are timed with the cam 208, the rotor 206, and the vanes 202 to provide flow into and out of the pumping chambers 214. The port plates also conduct the flow from the pumping chambers 214 into passages in the backing plates, which are connected to the appropriate inlet and discharge passages in a housing (not shown). The port plates are timed to substantially seal the major and minor dwell arcs 244, 246. The rotor 206 includes radial rotor slots 204 which allow radial movement of the vanes 202, allowing a line on the vane head 207 crown radius to remain in contact with the inner surface 210 as the vanes 202 are rotated by the rotor 206. The rotor vane slots 204 have terminal cavities 216 at the inboard end to provide clearance for the vanes 202 as they move radially inward in the discharge arcs 242 and also allow porting of fluid displaced by this vane motion in the inlet and discharge arcs 240, 242. The rotor 206 is rotated by the shaft 212 and urges the vanes 202 to rotate relative to the cam 208. The vanes 202 contact the inner surface 210 at a line on the crown radius to form a sliding seal with the inner surface 210, completing the pumping chambers 214.

FIGS. 3A and 3B are close-up cross-sectional diagrams of the example balanced clubhead vane pump 200. As can be seen in greater detail in these figures, the clubhead vane 202 includes a vane shank 306 that extends into the rotor slot 204, and a head 307 that extends substantially perpendicular to the vane shank 306 at a radially distal end of the vane 202, extending from the vane 202 in a generally trailing orientation relative to a direction of rotor rotation, as indicated by arrow 201. The head 307 includes a surface 319 formed with a crown radius 312. In general, to address the vane balancing problems of the pump 100 of FIG. 1, the geometry of the vane 202 is modified by controlling a crown radius axis 314 of the vane crown radius 312 relative to the edges 304, 308 of the vane 202 in conjunction with an edge 305 and an edge 309 of the rotor slot 204 edges relative to a center line of rotation 320 for the rotor 206. By controlling geometries of the tip of the vane 202, the crown radius axis 314, and the rotor slot edges 305 and 309, the contact point 302 between the vane crown radius 312 and the cam inner surface 210 can be controlled.

Referring to FIG. 3A, one of the clubhead vanes 202 of the example balanced clubhead vane pump 200 is shown in one of the major dwell arcs 244. The cam contact point 302 in the major dwell arc 244 is in advance of the trailing edge 304 of the vane shank 306, or trailing the leading edge 308 of the vane shank 306.

Selective design of the geometry of the vane 202 and the rotor slot 204 of the example balanced clubhead vane pump 200 can cause the contact point 302 in the major dwell arc 244 to be in advance of the trailing edge 304 of the vane shank 306, as indicated by dimension line 360, or trailing the leading edge 308 of the vane shank 306. Referring now to FIG. 3B, in the minor dwell arc 246 of the example balanced clubhead vane pump 200 the seal point 302 is located slightly forward or backward, as indicated by the dimension line 362, relative to the vane shank 306 due to changes in the cam 208 radii and tipping of the vane 202 in the rotor slot 204. In some embodiments, this change in the location of the sealing point 302 between the major dwell arcs 244 as shown in FIG. 3A, and the minor dwell arcs 246 as can be seen in FIG. 3B, can be used for improved vane hydraulic balancing, e.g., compared to the pump 100 of FIG. 1, since the vane shank 306 under-vane surface is ported to discharge pressure in the major dwell arc 244 or inlet pressure in the minor dwell arc 246, or vice versa, providing a slight hydraulic imbalance of the vane crown radius 312 into the cam inner surface 210 and provide a substantially positive seal between pumping chambers 214.

In the illustrated example balanced clubhead vane pump, the leading edge 309 of the slot 204 is radially aligned with the rotor centerline 320. The vane 202 is formed with an inverted “club head” vane shape, with the crown radius axis 314 selected to cause the contact point 302 to slightly lead the vane shank 306 trailing edge 304 plane when the vane 202 is in the major dwell arc 244. The “club head” shaped head 307 of the vane 202 overhangs the vane shank trailing edge 304. In some implementations, this vane 202 configuration can be referred to as having a “vane with trailing edge balance” (VTEB) and a rotor 206 with offset slots 204 having the “rotor slot leading edge on centerline” (RSLECL). In some embodiments, this type of geometry can provide numerous possible combinations of rotor slot 202 and head 307 balance points when compared to the leading edge 309 and trailing edge 305 locations relative to the centerline 320.

As illustrated by FIG. 3A, the vane 202 of the example balanced clubhead vane pump 200 is designed in conjunction with the cam surface 210 geometry and the rotor 206 such that, in the major dwell arcs 244 of the cam 208, the contact point 302 occurs on the surface 319, the small dimension 360, in advance of the projected plane of the trailing edge 304 of the shank 306 of the vane 202. A vane longitudinal axis of the vane 202, represented by the line AA, is offset from the central axis of the rotor and the rotational centerline 320. The contact point 302 provides the pressure seal point between high and low pressure, with the portion of the surface 319 in advance of the contact point 302 exposed to relatively high pressure and the portion of the surface 319 following the contact point 302 exposed to relatively low pressure.

Since the contact point 302 is in advance of the trailing edge 304 plane and the bottom of the vane shank 306 is exposed to high pressure, a small hydraulic imbalance is created urging the vane 202 into contact with the inner surface 210. Porting of the terminal cavity 216 maintains the bottom of the vane shank 306 substantially at discharge pressure in the major dwell arc 244. The geometry of the cam 208, vane 202, and rotor 206 controls the small angle between the rotational centerline 320, e.g., set by the rotor slot leading edge 309 substantially aligned with the centerline 320, and a conceptual line passing through the vane crown radius axis 314 by selecting the positions of both the rotor slot edges 305, 309, and the crown radius axis 314 to the vane shank edges 304, 308. The small dimension 360 on the crown surface 319 relative to the vane shank edges 304, 308 is decreased by the tipping angle of the vane 202 in the rotor slot 204. The dimensional relationship between the vane crown radius axis 314 and the edges 304, 308 of the vane shank 306 and edges 305, 309 of rotor slot 204 of the example balanced clubhead vane pump is selected to control this small angle and the location of the contact point 302 in advance of the vane shank trailing edge 304 plane. The combination of this small angle in conjunction with backward, e.g., cross corner, tipping of the vane shank 306 in the rotor slot 204 causes the contact point 302 to be located in advance of the vane shank trailing edge 304 plane as shown in FIG. 3A.

Referring to FIG. 3B, in one of the minor dwell arcs 246 of the example balanced clubhead vane pump, the seal point 302 on the surface 319 will shift slightly forward or backward relative to the vane shank 306 due to changes in the radii of the inner surface 210 and tipping of the vane 202 in the rotor slot 204. This change in the sealing point 302 between the major dwell arc 244 and the minor dwell arc 246 provides hydraulic balancing of the vane 202 since the vane shank 306 under-vane surface is ported to discharge pressure in the major dwell arc 244 or inlet pressure in minor dwell arc 246, or vice versa, to provide a slight hydraulic imbalance in these arcs urging the vane crown radius into the cam inner surface 210 to provide a substantially positive seal.

Still referring to FIG. 3B, the example balanced clubhead vane pump 200 is illustrated with the vane 202 positioned in the minor dwell arc 246. In the minor dwell arc 246 the vane 202 and the rotor 206 geometry results in a slightly larger angle which moves the contact point 302 on surface 319 toward the trailing edge 304 of the vane 202. The vane longitudinal axis represented by the line AA, is offset from the central axis of the rotor and the rotational centerline 320. The circumferential pressure forces acting on the vane 202 cause it to load onto the leading edge 309 of the rotor slot 204, in which the leading edge 308 of the vane 202 is substantially aligned with the slot leading edge 309, e.g., no tipping of the vane 202. This causes the contact point 302 to move to a position that is trailing the vane shank trailing edge 304 by the small dimension 362. In this configuration, the contact point 302 in the minor dwell arc 246 is at a point trailing the vane shank trailing edge 304 plane.

Since the under-side of the head 307 in this region is at discharge pressure, and the small dimension 362 is at low pressure a small imbalance force is generated to assist loading the vane 202 onto the inner cam surface 210. When the vane 202 is in the minor dwell arc 246, porting of the terminal cavities 216 maintains the bottom of the shank 306 at inlet pressure. In the inlet arcs 240 and discharge arcs 242, the under vane pressures are substantially matched to the over vane pressures as in a conventional pump, and there is substantially no hydraulic imbalance. Centripetal forces cause the vanes 202 to track the cam inner surface 210.

FIG. 4 is a cross-sectional diagram of another example balanced clubhead vane pump 400. The pump 400 is a dual lobe vane style positive displacement high pressure (HP) pump. The pump 400 includes a collection of clubhead vanes 402, each of the vanes 402 being located within a corresponding rotor slot 404 formed about the periphery of a rotor 406. The rotor 406 and vanes 402 revolve inside a cam 408. The rotor 406 is supported on a shaft 412.

A collection of pumping chambers 414 of the example balanced clubhead vane pump 400 are formed by two adjacent vanes 402, the inside surface 410 of the cam 408, the outside surface 430 of the rotor 406 and port plate axial surfaces (not shown). Pumping action is created by the change in length of the radius between the center of the shaft 412 and the inside surface 410 of the cam 408 between a smaller radius 420, e.g., minor radius, and a larger radius 422, e.g., major radius.

As will be shown in additional detail in FIGS. 5A and 5B, the example balanced clubhead vane pump 400 is substantially similar to the pump 200, except that the vanes 402 are reversed, e.g., the club-shaped heads protrude from the vane in the leading direction rather than in the trailing direction as they do in the example pump 200.

FIGS. 5A and 5B are close-up cross-sectional diagrams of the example balanced clubhead vane pump 400. As can be seen in greater detail in these figures, the clubhead vane 402 includes a vane shank 506 that extends into the rotor slot 404, and a head 507 that extends substantially perpendicular to the vane shank 506 at a radially distal end of the vane 402, extending from the vane 402 in a generally leading orientation. The head 507 includes a surface 519 formed with a crown radius 512. The geometry of the vane 402 is modified by controlling a crown radius axis 514 of the vane crown radius 512 relative to the edges 504, 508 of the vane 402 in conjunction with an edge 505 and an edge 509 of the rotor slot 404 edges relative to a center line of rotation 520 for the rotor 406. By controlling geometries of the tip of the vane 402, the crown radius axis 514, and the rotor slot edges 505 and 509, the location of the contact point 502 between the vane crown radius 512 and the cam inner surface 410 can be controlled.

Referring to FIG. 5A, one of the clubhead vanes 402 of the example balanced clubhead vane pump 400 is shown in a major dwell arc. The cam contact point 502 in the major dwell arc 244 is slightly in advance of a leading edge 508 of the vane shank 506, as indicated by dimension line 560.

Referring now to FIG. 5B, one of the clubhead vanes 402 of the example balanced clubhead vane pump 400 is shown in a minor dwell arc. In the minor dwell arc the seal point 502 is located substantially along the plane of the leading edge 508 of the vane shank 506, as indicated by the dimension line 562, due to changes in the cam 508 radii and tipping of the vane 402 in the rotor slot 404. In some embodiments, this change in the location of the sealing point 502 between the major dwell arcs and the minor dwell arcs can be used for vane hydraulic balancing since the full vane shank 506 under-vane surface is ported to discharge pressure in the major dwell arc or inlet pressure in the minor dwell arc, or vice versa, providing a slight hydraulic imbalance in these arcs of the vane crown radius 512 into the cam inner surface 510 and provide a positive seal between pumping chambers 414.

FIG. 6 is a cross-sectional diagram of another example balanced clubhead vane pump 600. The example clubhead vane pump 600 is a modification of the example balanced clubhead vane pump 200, in which the pressures within the collection of terminal cavities 216 can be substantially the same as the pressure in the pumping chamber 214 in advance of the vane 202. A rotor 606 is substantially similar to the rotor 206, with the addition of a collection of passages 602 in the rotor 606. The passages 602 communicate the pressures in the chambers 214 leading the vanes 202 into the under-vane terminal cavities 216.

FIG. 7 is a cross-sectional diagram of another example balanced clubhead vane pump 700. The example balanced clubhead vane pump 700 is another modification of the example pump 200, in which the pressures within the collection of terminal cavities 216 can be substantially the same as the pressure in the pumping chambers 214 in advance of a collection of vanes 702. The vanes 702 are substantially similar to the vanes 202, except that the vanes 702 include a fluid passage 704 on the leading edge of their vane shanks. The passages 704 communicate the pressures in the chambers 214 leading the vanes 702 into the under-vane terminal cavities 216.

In some embodiments of the example balanced clubhead vane pumps 600 and 700, by providing the passages 602 and/or 704, the ports of the under-vane terminal cavities 216 can be simplified. In some embodiments, the under-vane pressure and over-vane pressure can change proportionally, reducing possible over or under radial balances of the vanes 202 and/or 702. In some embodiments, the configurations of pump 600 and/or 700 can be used to reduce the need for under-vane kidneys in port plates and/or to reduce the need for port plates.

Although a few implementations have been described in detail above, other modifications are possible. For example, numerous other possible combinations of rotor slot edge positions relative to rotational centerlines and crown radius generation center points with respect to the vane shank edges may be used. In some embodiments, the vane crown radius contact points can be set to balance on either the leading edge or trailing edge of the vanes. In some embodiments, the balanced clubhead vane pumps 200, 400, 600, and/or 700 can be dual lobe cam fixed displacement vane pumps, single lobe fixed displacement vane pumps or multiple lobe fixed displacement vane pumps. In some embodiments, the design features described herein may also be applied to variable vane pumps implementing either single or multiple lobe style cams. In some examples, other components may be added to, or removed from, the described systems. Accordingly, other implementations are within the scope of the following claims. 

What is claimed is:
 1. A fluid pump, comprising: a housing comprising: an inlet port and an outlet port; a cam block having an inner surface comprised of two minor radii different from two major radii on the common center axis, and four developed curved surfaces connecting the two minor radii with the two major radii; a plurality of vanes, each vane comprising: a vane shank having a leading shank edge and a trailing shank edge; and, a vane head having a curved outer side, the curved side in contact with the cam block inner surface to separate a corresponding high fluid pressure region of a plurality of high pressure regions from a corresponding low pressure region of a plurality of low pressure regions; a rotor having a central axis substantially aligned with the center axis of the cam block inner surface and comprising: a plurality of vane slots, each vane slot comprising: a leading slot edge; a trailing slot edge substantially parallel to the leading slot edge, and spaced apart from the leading slot edge to accommodate the vane shank of one of the plurality of vanes; a cavity at the radial inboard side of each slot forming a fluid path within the vane slot; and fluid flow passages axially disposed on each side of the cam block with fluid passages communicating with the housing inlet and outlet ports and cavities formed by the cam inner surface, the rotor outside diameter and adjacent vanes and rotor cavities at the inboard side of each vane slot, wherein each vane of the plurality of vanes contacts the cam block inner surface at a contact point on the vane head controlled by the rotor vane slot position and the vane head outer curved surface, the contact point being located relative to the vane shank edge when the vane is radially aligned with the major radius and minor radius, and the contact point being located rotationally to create a controlled radial force between the vane head curved surface and the cam block inner surface.
 2. The fluid pump of claim 1 wherein, for each vane of the plurality of vanes, the vane shank has a vane longitudinal axis that is offset from the central axis of the rotor.
 3. The fluid pump of claim 1 wherein, for each vane of the plurality of vanes, the leading shank edge is substantially parallel to the leading slot edge when the vane is radially aligned with the minor radius, and the leading shank edge is tipped in the vane slot such that it is not parallel to the leading slot edge when the vane is radially aligned with the major radius.
 4. The fluid pump of claim 3, wherein an upper end of the vane shank is in contact with one of the leading slot edge or trailing slot edge, and a lower end of the vane shank is in contact with the other of the leading slot edge or the trailing slot edge.
 5. The fluid pump of claim 1 wherein, for each vane of the plurality of vanes, the vane head extends away from the trailing shank edge at an angle substantially perpendicular to the trailing shank edge.
 6. The fluid pump of claim 5, the rotor further comprising a plurality of fluid ports, each of the plurality of fluid ports in fluid communication between a cavity of a vane slot and a high pressure fluid region of the plurality of high pressure regions, substantially adjacent to the cavity.
 7. The fluid pump of claim 1, wherein the curved outer side is generated from an axis located on the leading edge of the vane shank.
 8. The fluid pump of claim 1, wherein the leading slot edge is substantially in radial alignment with the central axis.
 9. The fluid pump of claim 1, wherein the curved outer side is generated from an axis offset a predetermined distance in a direction of rotation from the leading slot edge. 